Image processing is often used for photography or movie. As we know, the scanner plays an indispensable role in this field. Increasing the resolution of a scanner is investigated hard in order to get more clear images, but high cost of a scanner with high resolution is not avoidable. The operating principle of the conventional scanner is shown in FIG. 1. An article is placed on the scanner to be scanned. The article is lit by a light source for generating an optical image 11. The optical image 11 of the article is focused on a charge coupled device 13 by a lens set 12, and then is converted to electronic signals to form digital data by the charge coupled device 13. For obtaining a higher resolution, the number of pixels for the charge coupled device 13 must be increased. However, the cost of the charge coupled device 13 is proportional to the square of the number of pixels for it. Requiring higher resolution will thus cost much since the cost of a charge coupled device 13 is a great part of the production cost of a scanner. Frankly speaking, it is difficult to spend lower cost for obtaining higher resolution in the first prior art.
Another method also has been developed to solve the problem of high-cost. Please refer to FIG. 2 showing the operating principle of a scanner according to the second prior art. The optical image of the scanned article is divided into two sections 211 and 212. There are any corresponding lens sets 221 and 222 and corresponding charge coupled devices 231 and 232 for the optical image sections 211 and 212 in this scanner. Different sections 211 and 212 are converted to electronic signals by the same steps as the first prior art by respective lens sets 221 and 222 and charge coupled devices 231 and 232. Finally, the electronic signals will be combined together to form a full image. Hence, the number of pixels for a charge coupled device is reduced, but the performance can be still maintained like that of the prior art. The cost can be reduced by this arrangement. However, the cost is proportional to the number of charge coupled devices. Accordingly, we still hope to make an improvement in increasing resolution and decreasing cost.